Method of tube manufacture



May ,8, 1928. 1,669,260

6 c. E. MAYNARD METHOD OF TUBE MANUFACTURE Filed May 27. 1926 Patented May s, v1928.

UNITED STATES vPATENT QFFICE.

oHAHLEs EDGAR HAYNARD, or Non'rHAnr'roN, '/MAssAoHusEcrrs, AssIGNon 'ro THE msx kunnen COMPANY, or oHroornn FALLS, MASSACHUSETTS, A con..

POBATION Ol' MASSACHUSETTS.-

METHOD OF TBE MANUFACTUBE.

Application led lay 27, '1926. Serial No. 111,988.

tion. It has for another object the elimination of all cutting of trimmings or scrap from the tube after vulcanization. It has for another object the improvement in the manner in which the tube is sealed to the mandrel in preparation forv vulcanization with its surface in direct Contact with a heated fluid such as steam. It has other and further objects which will appear from the following description and claims.

Referring to the drawings,

Fig. 1 is a plan view of a trimming and slriving table-upon which my invention may be practiced;

`1Eig..2 is an enlarged top plan view of a portion y thereof;

Fig. 3 is a side elevation of the portion of the device shown in Fig. 2;

Fig. 4 is a section on line 4 4 of Fig.- 3,

Fig. 5 is a sectional detail of a rubber tube prepared for vulcanization and ready for the skiving and trimming operation;

Fig. 6 is a similar view illustrating the completion of the skiving and trimming operation; and

Fig. 7 is 'a similar-view illustratingav modified way of preparing the tube for vulcanization.

In the manufacture of inner tubes for automobile tires it has been customary to vulcanize the tube upon a mandrel, remove it from the mandrel, skive the ends and join 'the tube into annular form. The purpose of the skive is to facilitate the s licing of the ends and to avoid sudden c anges in v.thickness in the wall of the completed tube.

Originally this skiving was done upon s ecially designed` cutting machines into which the ends of the vulcanized tubes were inserted after removal from the mandrel. More lately it has been proposed to make the y.

skive during vulcanization by some species of clamp or culi' which molded th'e end of the tube against the mandrel as the tube was being cured, as in my Patent No. 1,391,784

length of the tube being initially greater than that ultimately desired, with a consequent trimminv of the tube after it has been vulcanized. he trimming or scrap thus produced, being of vulcanized rubber and therefore being incapable of re-use without undergoing a reclaiming or desulphurizing process, is worth less 'to a rubber manufacturer than the same amount of scrap in unvulcanized form. Further proposals have therefore been made, 'by which the tube was skived by clamps or cuffs left Vonduring vulcanization and the tube trimmed to length prior to vulcanization either by the cuits themselves or by a knife.

These prior proposals have all been objectionable for one reason or another, because of extra operations involved, the production of cured scrap, or the expense and labor incident upon'the use of clamps or culs. By my invention I am enabled to avoid these awkward and expensive prior methods, and to cut the tubes to length and skive them at one operation without the use of clamps or cuits during vulcanization. In another aspect of my invention I prepare the tubes for vulcanization in a better manner than has hitherto been done, avoiding the use of expensive equipment during vulcanization and eilectively preventin the formation of blemishcd or defective tu es by the entrance ofthe vulcanizing fluid between the tube and the mandrel.

Stated rather brieily, my invention comprises in one aspect trimmlngthe end of the tube, while still uncured and mounted on the mandrel, by a knife shaped and mounted so as to cut upon a bevel, thus skiving the tube and cutting it to length in one operation. In another aspect my invention comprises skiving the tube around a circumference where a layer of adhesive rubber has been placed between the tube and the mandrel, thereby forming a tight seal up to the very edge of the skive without the necessity for using any external confining means such as clamps or cuffs. In still another aspcct of my invention I supplement the scaling action ot the cement by a thin and therefore inexpensive band of elastic rubber. which may be of insuiiicient strength to do the actual skiving.

In the drawings I have shown a device by which the method described above may be practiced. Upon a table 10 are secured journals .11 for spaced pairs of rolls 12, these rolls serving to support rotatably a tube mandrel 13. 'Preferably one of these rolls carries a sprocket 14 connected by a chain 15 to a sprocket on a power shaft 16. Of 'course other means of rotating the rolls may be used, or the rolls may be free yand the mandrel rotated upon them by hand. In case the mandrel is to be rotated by the rolls, it is preferably held against them by a roll 17 carriedas on a swinging arm 18 and pressed against the mandrel by a spring 19. Driving means have been shown at one end only of the mandrel, but if desired it may be rotated from both ends.

Mounted upon a bracket 20 at each end of the table is an electric heating element 21 of any usual type, such for example asis employed in electrically heated soldering irons. A heavy metal heat conducting body 22 projects from this heating element and is s lit to receive a cutting blade 23. This bla e is preferably formed of some metal such as bronze which combines the features of high heat conductivity and wearing qualities. The cutting edge of the blade is shaped so that at one end 24 it comes in contact with the mandrel while the other end 25 is spaced a short distance away. Intermediate these points the blade is curved both away from the mandrel surface and longitudinally of the mandrel, so that be along a ta er. As the mandrel revolves, the rubber tu e 26 upon it is drawn past the knife which is preferably heated to a. tem perature suiicient to soften the rubber and acilitate the cutting. The tube is thus simultaneously cut and skived along the line 27, the trimmed end 28 being now removable, leaving the end of the tube beveled off as at 29 in Fig. 6. As stated before, it isA one object of my lnvention to improve the sealing of the tube to the mandrel. This is of importance in methods of tube vulcanization in which the tube is exposed to the action of a heated fluid such as steam. In this connection I make use of, and in certain aspects improve upon, the disclosure in my copending application Serial No. 102.458, filed April 16, 1926, in which a band of cement or other adhesive rubber is applied between the tube and the mandrel. This band of rubber is indicated in the present drawings at 30. Preferably the skive is made so that it passes through the cement. the combination of the heat of the knife, the drawing o1' shearing nature of the cut and the pressure with which the knife is forced against the Inandrel making a perfect seal at this point and insuring that the tube will be stuck securely to the cement, As a further safeguard I may place over the end of the tube a short the cut made will or displacement of the thin edge of the tube l 26 during the cure.

By using one of these cutting and skivlng units on each end of the mandrel, the tube will be trimmed accurately to length and both ends beveled off as a single operation. In order to align the mandrel accurately with the cuttingdeviees, I. preferably provide at one end a sto 32 against Iwhich the end of the mandrel a uts. Adjustability of the stop to accommodate different sizes of tubes can be secured by making it slidable in guides 33, with a thumb screw 34 for holding it in adjusted position.

The mechanical structure here shown is illustrative only, changes in design being contemplated within wide limits. The scope of the inventoin, in its aspects both as a method and as a machine, is pointed out in the appended claims.

Having thus described my invention, I claim:

1. A method of making a rubber tube which comprises beveling the end of the tube with an edged tool while the rubber is as yet uncured, and subsequently vulcanizing the rubber.

2. A 'method' of making a rubber tube which comprises forming a piece of tubular stock with open ends, interiorly supporting the tube adjacent its end, beveling the end of the tube with an edged tool, and subsequently vulcanizing the rubber.

3. A method of making a rubber tube which comprises mounting a length of tubular stock upon a mandrel, beveling at least one end of the tube by severing the uncured rubber with an edged tool acting against the mandrel, sealing the ends of the tube to the mandrel, and subjecting the tube to vulcanization.

4. A method of making a rubber tube which comprises mounting the tube on a mandrel with a film of adhesive rubber between the tube and mandrel at each end, trimming the tube to length by a shearing cut passing through the tube and rubber lm at each end, whereby the tube is tightly sealed to the mandrel. and subjecting the tube to vulcanization in an atmosphere of heated fluid.

5.. A method of making a ,rubber tube which comprises mounting the tuf e on a mandrel with a film of adhesive rubber between the tube and mandrel at each end, bevellng the ends of the tube and simultaneously. trimming the tube to length by a shearing cut passing through the tube and rubber lm at each end, whereby the tube lms 7. A method of vulcanizing a rubber tube which comprises mountin the tube upon a mandrel with a film of a hesive rubber between the tube and the mandrel at each end, cutting the tube on a bevel vat each end, the cut passing through the film of adhesive 15 rubber, binding the ends of the 4tube to the mandrel by an elastic band, and subjecting the tube to a. vulcanizing heat.

CHARLES EDGAR MAYNARD. 

